【正文】 大學(xué)生活至此劃上了圓滿的句號，在天津工程師范學(xué)院這塊土地上有眾多莘莘學(xué)子辛勤的耕耘，在這塊土地上我健康快樂的成長，我永遠(yuǎn)不會(huì)忘記可親的同學(xué)，我永遠(yuǎn)記得這片土地。致謝經(jīng)過兩個(gè)月的畢業(yè)設(shè)計(jì)忙碌之后，設(shè)計(jì)最終完成，心理有一種說不出的輕松，設(shè)計(jì)過程中遇到許多的問題，在眾多師友的幫助下予以解決。必須能夠預(yù)見和防止諸如不同的螺紋孔的螺釘之間的干涉和不同的連桿機(jī)構(gòu)之間的干涉。軸肩和導(dǎo)向表面在裝配過程中不需要測量就能提供準(zhǔn)確定位。6. 保證零件在裝配中準(zhǔn)確定位和不發(fā)生干涉。在其它情況下，若機(jī)器設(shè)計(jì)人員自己來設(shè)計(jì)零件，則零件的強(qiáng)度，可靠性和成本等方面的要求就可以更好的得到滿足。若一個(gè)以前研制的零件能夠滿足性能要求和可靠性要求，并適合與所設(shè)計(jì)的那臺機(jī)器而無須附加的研制費(fèi)用，那么設(shè)計(jì)人員及其公司通常會(huì)從零件制造廠的現(xiàn)貨中選取該零件。成本和制造性能都是應(yīng)該考慮的因素，這些因素包括可焊接性，機(jī)械加工性能，對熱處理溫度變化的敏感性和所需要的涂層等。當(dāng)數(shù)據(jù)不完全時(shí)，可以應(yīng)用理論公式作為尺寸的指南，在擴(kuò)展后的范圍內(nèi)獲得令人滿意的設(shè)計(jì)結(jié)果4. 根據(jù)性能組合選擇材料。例如，對于薄壁鋼管，考慮到腐蝕性，可以將根據(jù)壓力求得的厚度增加一些。例如，用梁的表面應(yīng)力公式來計(jì)算齒輪的輪齒尺寸。力學(xué)和其他學(xué)科的基本公式是公認(rèn)的計(jì)算依據(jù)。避免產(chǎn)生共振。曲軸，凸輪軸以及含有軸承支座的外殼和構(gòu)架都應(yīng)有足夠的剛度以保證直線對中精度和接觸表面之間的壓力均勻分布。改變零件的形狀，可以降低它所承受的應(yīng)力，對零件施加預(yù)應(yīng)力，如表面滾壓和淺表面硬化，均可以使其得到強(qiáng)化。2. 載重量最輕的情況下，提供合理的應(yīng)力分布和剛度。離合器結(jié)合面上需要有摩擦，而離合器軸承卻不需要摩擦。一種性能在某種場合下可能是有用的，而在另外一種場合下則可能是有害的。1. 創(chuàng)造性的利用所需要的物理性能和控制不需要的物理性能。銷售吸引力，客戶的滿意程度和制造成本均與設(shè)計(jì)有關(guān)，而設(shè)計(jì)能力則與工程創(chuàng)新的實(shí)現(xiàn)是密切相關(guān)的。如果試驗(yàn)結(jié)果令人滿意，而且該裝置將要進(jìn)行批量生產(chǎn)，就應(yīng)該對最初提出的設(shè)計(jì)方案做一些修改，使其能以較低的成本進(jìn)行批量生產(chǎn)。這些分析包括根據(jù)靜力學(xué)原理分析反作用力和充分利用摩擦力，根據(jù)動(dòng)力學(xué)原理分析慣性，加速度和能量；根據(jù)彈性力學(xué)和材料力學(xué)分析應(yīng)力和變形；根據(jù)流體力學(xué)來分析潤滑和流體傳動(dòng)。要對材料和處理方式進(jìn)行選擇。分析工作的目的是要在重量最輕，成本最低的情況下，獲得令人滿意，即優(yōu)良的工作性能，并且還要安全耐用。對于此項(xiàng)工作，徒手畫的草圖是很有價(jià)值的，它不僅可以記錄下我們的想法，而且還有助于與別人進(jìn)行討論，特別是和自己的大腦進(jìn)行交流，從而促進(jìn)創(chuàng)新想法的產(chǎn)生。對于現(xiàn)有的設(shè)備可能需要在耐用性，效率，重量，速度或者成本等方面做進(jìn)一些改進(jìn)工作；也可能要新的設(shè)備完成以前由人來做的工作，例如計(jì)算或者裝配?？偸谴嬖谥玫姆椒▉硗瓿稍O(shè)計(jì)工作，設(shè)計(jì)人員應(yīng)該不斷努力，尋找這些更好的方法。有時(shí)，在產(chǎn)品的裝配時(shí)或者裝箱外運(yùn)前的實(shí)驗(yàn)中才發(fā)現(xiàn)設(shè)計(jì)中的某種缺陷?？赡芤髮δ硞€(gè)零件尺寸或公差做一些更改，使零件的生產(chǎn)變得容易。設(shè)計(jì)工程師還應(yīng)該通過零件圖和裝配圖，與制造部門一起對最終設(shè)計(jì)方案進(jìn)行溝通。為了進(jìn)行有效的交流，需要解決下列問題：（1） 所要設(shè)計(jì)的這個(gè)產(chǎn)品是否真正為人們所需要？（2） 此產(chǎn)品與其它公司的現(xiàn)有同類產(chǎn)品相比有無競爭力？（3） 生產(chǎn)這種產(chǎn)品是否經(jīng)濟(jì)？（4） 產(chǎn)品的維修是否方便？（5） 產(chǎn)品有無銷路？是否可以盈利？只有時(shí)間才能對上述問題給出正確的答案。從一次失敗中可以學(xué)到很多東西，只有不怕遭受失敗的人才能取得最大的收獲。如果上述三種能力都較差，那就永遠(yuǎn)沒有人知道他是一個(gè)多么能干的人！一個(gè)有能力的工程師不應(yīng)該害怕在提出自己的方案是遭到失敗的可能性。因此，一個(gè)優(yōu)秀的工程師除了掌握技術(shù)之外，還應(yīng)該精通這三種表達(dá)方式。只有成功地完成這項(xiàng)工作，為得出這個(gè)方案所花費(fèi)的大量時(shí)間和精力才不會(huì)被浪費(fèi)掉。提出方案是一種說服別人的工作。與其他人就設(shè)計(jì)方案進(jìn)行交流和溝通是設(shè)計(jì)過程的最后和關(guān)鍵階段。這并不是一項(xiàng)容易的工作，因?yàn)閷?shí)際上并不存在著一個(gè)對所有人來說都是最優(yōu)的操作范圍和操作過程。心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機(jī)器。通常要提出幾套設(shè)計(jì)方案，然后加以比較。即使產(chǎn)生了許多不切合實(shí)際的想法，也會(huì)在設(shè)計(jì)的早期，即繪制生產(chǎn)圖紙之前被改正。應(yīng)該強(qiáng)調(diào)的是，如果設(shè)計(jì)本身不要求采用全新的方法，就沒有必要僅僅為了變革的目的而采用新辦法。新設(shè)計(jì)本身會(huì)有許多缺陷和未能預(yù)料的問題發(fā)生，只有當(dāng)這些缺陷和問題被解決之后，才能體現(xiàn)處新產(chǎn)品的優(yōu)越性。由于許多人墨守成規(guī)，這樣做并不是一件容易的事情。因此，設(shè)計(jì)人員必須要有耐心，因?yàn)樗ㄙM(fèi)的時(shí)間和努力并不能保證帶來成功。例如，即使將一個(gè)小數(shù)點(diǎn)的位置放錯(cuò)，也會(huì)使正確的設(shè)計(jì)變成錯(cuò)誤的。僅僅使用數(shù)據(jù)和公式是不足以在一個(gè)好的設(shè)計(jì)中作出所需的全部決定的。應(yīng)當(dāng)把機(jī)械設(shè)計(jì)看成設(shè)計(jì)人員運(yùn)用創(chuàng)造性的才能進(jìn)行產(chǎn)品設(shè)計(jì)，系統(tǒng)分析和制定產(chǎn)品的制造工藝的一個(gè)良機(jī)。發(fā)明，發(fā)現(xiàn)和科學(xué)知識本身并不一定能給人來帶來益處，只有當(dāng)它們被用在產(chǎn)品上才能產(chǎn)生效益。設(shè)計(jì)工程師不僅在工作上要有創(chuàng)新性，還必須在機(jī)械制圖，運(yùn)動(dòng)學(xué)，動(dòng)力學(xué)，工程材料，材料力學(xué)和機(jī)械制造工藝等方面具有深厚的基礎(chǔ)知識。進(jìn)行各種機(jī)械設(shè)計(jì)工作的人員通常被稱為設(shè)計(jì)人員或者設(shè)計(jì)工程師。 friction is desired at the clutch face but not in the clutch bearing. Ingenuity in design should be applied to utilize and control the physical properties that are desired and to minimize those that are not desired.2. Provide for favorable stress distribute and stiffness with minimum werght.On ponents subjected to fluctuating stress, particular attention is given to a reduction in stress concentration, and to an increase of strength at fillets, threads, holes, and fits. Stress reduction are made by modification in shape ,and strengthening may be done by prestressing treatments such as surface rolling and shallow hardening. Hollow shafts and tubing, and box sections give a favorable stress distribution, together with stiffness and minimum weight. Sufficient stiffness to maintain alignment and uniform pressure between contacting surfaces should be provided for crank, cam, and gear shafts, and for enclosures and frames containing bearing supports. The stiffness of shafts and other ponents must be suitable to avoid resonant vibrations.3. Use basic equations to calculate and optimize dimensions. The fundamental equations of mechanics and the other sciences are the accepted bases for calculations. They are sometimes rearranged in special forms to facilitate the determination or optimization of dimensions, such as the beam and surface stress equations for determining geartooth size. Factors may be added to a fundamental equation for conditions not analytically determinable, . , on thin steel tubes, an allowance for corrosion added to the thickness based on pressure. When it is necessary to apply a fundamental equation to shapes, materials, or conditions which only approximate the assumptions for its derivation, it is done in a manner which gives resuluts “ on the safe side”. In situations where data are inplete, equations of the sciences may be used as proportioning guides to extend a satisfactory design to new capacities. 4. Choose materials for a bination of properties. Materials should be choose for a bination of pertinent properties, not only for strengths, hardness, and weight, but sometimes for resistance to impact, corrosion, and low or high temperatures. Cost and fabrication properties are factors, such as weldability, machinability, sensitivity to variation in heattreating temperatures, and required coating. 5. Select carefully between stock and integral ponents. A previously developed ponents is frequently selected by a designer and his pany from the stocks of parts manufacturers, if the ponent meet the performance and reliability requirements and is adaptable without additional development costs to the particular machine being designed. However, its selection should be carefully made with a full knowledge of its properties, since the reputation and liability of the pany suffer if there is a failure in any one of the machine’s parts. In other cases the strength, reliability, and cost requirements are better met if the designer of the machine also designs the ponent, with the particular advantage of pactness if it is designs integral with other ponents, . , gears to be forged in clusters or integral with a shaft. 6. Provide for accurate location and noninterference of parts in assembly. A good design provides for the correct location of parts and for easy assembly and repair. Shoulders and pilot surfaces give accurate location without measurement during assembly. Shapes can be designed so that parts cannot be assembled backwards or in the wrong place. Interferences, as between screws in tapped holes, and between linkages must be foreseen and prevended. Inaccurate alignment and positioning between such assemblies must be avoided, or provision must to minimize